sedimentary

Chert (often called Flint when found in chalk)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: tan, brown, or greenish-yellow with waxy luster. Microcrystalline structure with conchoidal (shell-like) fracture. Generally opaque to translucent.

Color: tan, brown, or greenish-yellow with waxy luster

Identified May 24, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: tan, brown, or greenish-yellow with waxy luster. Microcrystalline structure with conchoidal (shell-like) fracture. Generally opaque to translucent.

Formation & geological history

Formed through the precipitation of silica in sedimentary environments, often replacing organic material or filling cavities in carbonate rocks. Can be millions of years old, often from the Cretaceous period.

Uses & applications

Historically used for stone tools and strike-a-lights. Currently used in road surfacing, decorative landscaping, and occasionally as a gemstone in tumbled form.

Geological facts

Because of its hardness and the way it fractures into sharp edges, it was the primary material for spearheads and arrowheads during the Stone Age.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy feel, and smooth curved fracture surfaces. Commonly found in gravel beds, riverbanks, and coastal regions with chalk deposits.